The enzyme and substrate must fit together like a lock and a key. If the fit is not exact the reaction will not occur. The diagram below shows the lock and key theory:
Overall, substrate concentration will only increase the reaction rate until all of it is bound to enzyme molecules. Enzymes must bind with a substrate and form an enzyme substrate complex before products can be produced. If the concentration of substrate is low, enzymes will bind with all the substrate. The remaining enzymes will be unable to bind with any substrate and the reaction rate will not increase until more substrate is added. The diagram below demonstrates this:
Fair Testing
Key Variables
I will keep these variables constant:
-Concentration of starch
-Concentration of amylase.
-Temperature.
-Volume of Solutions.
-Amount of iodine.
I will change these variables:
-Concentration of amylase (already adjusted into neutral PH)
Preliminary work
Before I did the method I used a spotting tile technique to see how amylase breaks down starch and here are my results:
I have spotted many errors for example the reaction time was 30 seconds and reaction to finish within these 30 seconds. Also the volumes of solutions were so small that it was different to make any logical judgement, so I decided to have a more accurate method.
Apparatus
For this experiment I need specific equipment:
-Safety goggles
-30ml of Amylase
-50ml of Starch
-Pipette
-10ml measuring cylinder
-50ml beaker
-Glass stirring rod
-Spotting Tile
-Iodine Solution
-Two boiling tubes
-Stopwatch
Method
- Firstly using a pipette I will pour 10ml of Starch into a 10ml measuring cylinder and then pour it into a boiling tube.
- Then I will thoroughly rinse out the pipette and measuring cylinder with water.
- Then I will put the amount of amylase needed in the measuring cylinder again using the pipette to make it exact and then transfer it to an empty boiling tube along with the correct amount of water needed.
- I’ll then add iodine into the boiling tube of 10ml of starch and mix it with a stirring rod.
- I’ll mix the iodine and starch solution with the water and amylase solution and time it with a stopwatch.
- I will time how long it takes for the enzymes to break down the starch. To be able to tell when this is finished is when the solution goes clear.
- Once this process finishes I will record my results and repeat it again for my second try, to make it a fair test.
- I will then wash out both boiling tubes, the measuring cylinder and the pipette and repeat the process with different amylase and water concentrations.
Here is a table of concentrations I am going to use and repeat each twice:
I am going to make this experiment safe by wearing safety goggles every time I am dealing with harmful chemicals like iodine, I am going to make sure I don’t spill any thing on the table any not let the chemicals go on to my skin, if they do I will ensure that I thoroughly wash my hands. All bags and clothing should be kept away from the experiment work surface. Long hair should be tied up. All apparatus should be handled with care as a lot of glassware is being handled which if broken can be very hazardous.
Results
These are my results of how long the amylase concentration took to turn colourless. I repeated my experiment to make the results as accurate and as fair as possible.
Evaluation
I think that my investigation was quite successful as my prediction turned out to be correct. The average time of each reading fully supports my prediction however on some readings on my 2nd try they come up to be different from my prediction. For example when my amylase concentration was 1.0% on my 1st try the time taken for the blue to disappear was 26.50seconds and on my 2nd try it was 7.34seconds. The second time in comparison to my first time was very short and it could have been caused by an error like not washing up the old solution thoroughly, there could have still been some amylase solution left and that would have made the reaction occur more quicker.
My results table shows that my prediction was correct. The rate of reaction increases as I increase the concentration of amylase. Also, as the amylase concentration goes higher, the time taken for the blue colour to disappear goes quicker. This is because the more amylase put into the solution the more collisions there will be. The diagram in my prediction explains this theory.
I think that my results aren’t 100% accurate due to parallax error, which is an error that can occur if the reading is not read in line with the level of liquid. Also, I think that the iodine can affect how fast the solution changes colour; throughout the experiment I should use the same iodine concentration. Also I could have left some of the solution in the test tube if I didn’t wash it properly, to avoid this happening again I could use different test tubes for each time I repeated the process. My measurements are preferably within 5% of the true value. The experiment took place over two days, in which the room temperature could have varied within the two days, making the test unfair. The results were also determined by looking at when the solution turns colourless, however when this process took place I believe that I may have had misinterpretations of the colours
If I were to repeat the investigation I would change part of the method by instead of making two attempts I would make three in order to make my results more accurate, this would also get me more information but I would have needed more time to do my experiment. However to be certain this extra work might just give me more of the same information rather than new information. Also if I had more boiling tubes preferably two for each concentration it would have made my results more accurate and my evidence would be more reliable.
Generally I didn’t meet any difficulties during the investigation I found the whole experiment quite straightforward.
Bibliography
To provide myself with the information I needed for this investigation I used textbooks and the Internet. I found the Internet a lot more helpful as it provided a wide range of helpful sites. I went on and just entered which parts I needed help on and easily got search results.
Analysis
The first part of my analysis was having to work out the average time for my results. I did this by adding my 1st try and 2nd try together and dividing it by two. For example my 1st try was 107secs and my 2nd was 42.78secs. I would add them together and divide them by 2 to leave me with an answer of 74.89secs. I then had to work out my rate of reaction. I would do this by dividing the average time by 1. In this case I would do 1/74.89, which would leave me with an answer of 0.013. This would be my rate of reaction.
I also had to put the information of my average time and the information of my rate of reaction into scatter graphs. I put my information into scatter graphs as they are easy to read and it is an easy method to set out my information. My first graph was a graph to show the average time taken for amylase to dissolve. It shows that as the amylase concentration level went up the average time dropped. My second graph shows the rate of reaction for amylase concentrations. It shows that the rate of reaction increases as the concentration of amylase increases. I noticed was that when I added more amylase concentration the faster the solution turned colorless. This is because of the collision theory since the particles collide more due to high concentration of amylase. This observation backs up my prediction.
In graph number one there is a big increase between the reading of 0.5% concentration and 1.0% amylase concentration as the time the amylase took a lot less to make the amylase dissolve this could be because of using more amylase than needed and these results may not be proper accurate.
In graph number two there is a large difference between 1.5% of amylase concentration and 2.0% of amylase concentration. The 2.0% has a lot larger rate of reaction than 1.5%. This difference could be caused by minor errors like parallax error during the investigation. If the rate of reaction goes higher than it should, it could be that I have used too much amylase. If there were more amylase the rate of reaction would be higher. Apart from these minor errors my results do back up my prediction. In my first graph I see a negative correlation pattern and in my second graph I see a positive correlation pattern.